Lice in Horses

Lice are widespread parasitic pests that can infest many animals' coats, including horses. They typically target horses that live in overcrowded, unsanitary conditions or those that are stressed for any number of reasons. There are two species of lice and the distinction is how they feed: one species feeds through biting and chewing on hair and dead skin, while the other feeds through sucking the blood of the host animal. Both cause extreme itching and skin damage due to horses scratching their irritated skin.

What Are Lice?

Lice are tiny parasitic insects that live in the hair coat of horses and other mammals. Lice infestations can be an indication of poor care and/or poor nutrition, but they occasionally occur for no apparent reason. They can be common in stables where close quarters and shared equipment make the spread of lice easy. 

The two species of lice that impact horses are Haematopinus asini (H. asini), the blood-sucking type, and Damalinia equi (D. equi), the skin biting type.

Symptoms of Lice in Horses

Lice like to breed in horses' thick winter coats, but they can be present year-round. They will migrate all over the horse's body, including the mane and tail. Wherever they are, they cause horses a lot of discomfort.

A lice-infested horse will be intensely itchy, especially around the base of the tail, mane, and head. The lice lay eggs called nits in the horse's hair coat and mane. These nits will hatch into nymphs that mature into egg-laying adults. Both nymphs and adults will cause the itching associated with lice. As the horse tries to relieve the itching by rubbing itself on fences, trees, or stall walls, it can rub raw patches on its skin.

A horse can be so uncomfortable that it will appear listless or colicky and become very run down. Depending on the type of lice, the parasites will either suck the horse's blood or feed off of dead skin cells, both of which are itchy. If the horse is infested with the sucking louse, blood loss may be severe enough to cause anemia, which will make the horse feel lethargic.

Causes of Lice

Typically, horses that are underweight or in poorer condition are more susceptible to lice infestations. Healthy horses have a stronger immune system and can usually fight off an infestation unless they are housed in stressed or poor conditions. Other potential causes of lice include:

• Physical contact with another lice-infested horse
• Using tack or grooming tools that are lice-infected

Diagnosing Lice in Horses

Lice are generally diagnosed based on symptoms and the presence of nits (eggs), which are visible to the naked eye. If no nits are seen, then a veterinarian may also perform a skin scraping to check for parasites under a microscope because mange can cause similar symptoms.

Treatment

The first step is to treat the horse with either a topical de-lousing powder or medication. Common treatments are permethrin-based dust, shampoos, or rinses. Be cautious when applying treatment to irritated skin because it may sting.

When applying any medication powder, take care not to inhale it, and to wash up after you apply it. Wear gloves and a dust mask to avoid contact with the chemicals.

All equipment that could carry lice or nits must be washed as well. Blankets and washable equipment can be laundered and dried with high heat, or even boiled.

Prognosis for Horses with Lice

With help and treatment, a horse is likely to recover from lice without much concern. The bigger challenge is making sure your horse is healthy and has comfortable living conditions to reduce stress and the likelihood of lice infestations.

Lice are species-specific, meaning that bird lice generally don't live on people or dogs, and horse lice don't typically infect people. Neither you nor your other pets are likely to get lice from your horse. The lice are transferred from horse to horse by direct contact or through shared brushes, blankets, and equipment.

How to Prevent Lice

The best way to ward off lice is to keep your horse in spacious, sanitary conditions and feed it a nutritious diet.

If you bring a new horse home, it should be kept separate from other horses to prevent any problems, including lice, to the resident herd. In a busy barn, it's a good idea that each horse has its own brushes and equipment because shared grooming tools and blankets can spread many skin problems like lice, ringworm, and mange.